A. Field of the Invention
The invention relates to a new configuration of clutch disk assembly, and more particularly, to new configuration for attaching friction material to outer radial portions of a clutch disk assembly.
B. Description of the Background Art
A clutch disk assembly used in a clutch mechanism of a vehicle includes a pair of circular input plates and an output hub having a radial flange. Elastic members are disposed between the input plates and the flange for restricting relative rotation therebetween. A clutch disk (sometimes referred to as frictional coupling portion) is formed with at least one cushioning plate between two friction facings. The clutch disk is disposed on a radially outside portion of the pair of input plates.
In some clutch disks of a clutch disk assembly, a plurality of cushioning plates between the two friction facings. The cushioning plates are disposed circumferentially about the outer periphery of the clutch disk assembly, and the two friction facings are arranged on axially opposite sides of the cushioning plates. Each cushioning plate has a fixing portion coupled to one of the input plates, e.g., by rivets, and a cushioning portion arranged between the two friction facings. The cushioning portion has a wavy section, and is deformable between the two friction facings. More specifically, the cushioning portion has a first portion arranged on one of the friction facings, a second portion arranged on the other friction facing, and a coupling portion coupling the first and second portions together. The first and second portions are axially shifted from each other so that the cushioning portion can be bent and deformed as compressive forces are applied to the friction facings during clutch engagement. The compressibility of the cushioning portion provides a cushioning effect.
In the conventional clutch disk described above, the first and second portions of the cushioning plates are fixed to the friction facings by rivets. Therefore, the friction facing cannot have a sufficiently large effective service thickness because the heads of the rivets have a minimal thickness that extends in an axial direction effectively limiting the useable thickness of the friction facing.
The friction facings of some clutch disks are formed from an organic (chemical) material and some friction facings are formed from an inorganic (metallic) material.
The metallic material is used in heavy weight vehicles and racing cars because the metal has high resistances against a heat and a surface pressure. The metallic material typically contains copper powder as its main component, and also contains tin, lead, graphite or the like as additive. The friction facing made of the metallic material is produced by heating and sintering a mixture of the foregoing materials, and the core plate is fixed thereto during the sintering. Cera-metallic facings utilizing ceramics have also been developed as the friction members made of a metallic material.
The clutch disk made of an organic material is somewhat compressible in use as a friction member and therefore may provide some cushioning effects in a clutch disk assembly. However, the clutch disk provided with such metallic friction members made of sintered alloy cannot provide a cushioning effect because the metallic material is generally not compressible. Therefore, a large shock is experienced when the clutch mechanism moves from a dis-engaged state to an engaged state. Therefore, smooth start of the vehicle is difficult. For similar reasons, shudder (abnormal vibration) and noises of the clutch are liable to occur.
For overcoming the above problems, a cushioning plate may be disposed between a pair of friction members for providing the cushioning effect. In this case, one of the friction disks is fixed to a clutch plate (part of the clutch disk assembly), and the other is fixed to the cushioning plate by rivets. However, heads of the rivets may restrict the maximum cushion quantity (i.e., the maximum allowable degree of cushioning), or may reduce the effective service thickness of the friction member. Further, the rivets increase a weight and therefore a moment of inertia of the clutch disk.